103 



but one sole formation. The presence of cyanite, 

 rutile-titanite, and garnets, and the absence 

 of lydianstone, and all fragmentary or arena- 

 ceous rocks, seem to characterize the formation 

 we describe as primitive. It is asserted, that 

 even in Europe ampelite and greenstone are 

 found, though rarely, in slates anterior to tran- 

 sition-slate. 



When, in 1785, after an earthquake, a great 

 rocky mass was broken off in the Aroyo del 

 Robalo, the Guaykeries of los Serritos collected 

 fragments of alum five or six inches in diameter, 

 extremely pure and transparent. It was sold in 

 my time at Cumana to the dyers and shoemakers, 

 at the price of two reals (one quarter of a piastre) 

 a pound, while alum from Spain cost twelve reals. 

 This difference of price was much more the effect 

 of prejudice, and the shackles of trade, than of 

 the inferior quality of the alum of the country, 

 which is used without undergoing any purifica- 

 tion. It is also found in the chain of micaslate 

 and clayslate on the north-west coast of the 

 island of Trinidad, at la Margaretta, and near 

 cape Chuparuparu, north of the Cerro del Dis- 

 tiladero # . The Indians, naturally addicted to 



* Another place was indicated to us, west of Bordones, 

 the Puerto Escondido. But that coast appeared to me to be 

 wholly calcareous ; and 1 cannot conceive where could be 

 the situation of ampelite and native alum on this point. Was 

 it to be found in the beds of slaty clay, that alternate with 



